The 1,900-year-old bridge, which straddles the river Cadnant, near Rhosbodrual, Caernarfon had its sides “partially destroyed” during the half term school break on Monday, February 16.

It is the third time the bridge has been targeted in three years and Cadnant ward councillor Huw Edwards is “fed up” with the “mindless” actions of those responsible.

Cllr Edwards said: “Stones were knocked off the sides of the bridge into the river below and it will be closed for around three weeks as a result.

“The bridge is a valuable piece of the town’s legacy and a site of historic significance which is still used today and means so much to many people in the community.”

The councillor had received reports from local residents that younger teenagers, aged between 12-13, were seen in the area.

“I would appeal to whoever is carrying out this mindless vandalism to stop doing it. Not only have they partially destroyed the bridge but made it too dangerous for children and young families to use now.”

Caernarfon-based police community support officer Geraint Williams said local officers would be stepping up patrols in the area in a bid to deter any further acts of vandalism.

Caernarfon Civic Society chairman Hywel Roberts said he was “very concerned” that the bridge had been damaged once again.

He said: “It is a well preserved example of a humped back bridge which is still in use today and needs to be protected.”

A Gwynedd Council spokesman said: “We are aware of concerns regarding damage that has been caused to this particular footbridge on a number of occasions in the past, and the council has always arranged remedial work to repair any damage.

“On this occasion, more substantial damage has occurred, and the council is considering undertaking further remedial work which could involve the temporary closure of the footbridge.

“We would urge members of the public to respect their local environment, and would ask anyone who witnesses any act of anti-social behaviour to contact the police.”